Radio beacon of complementary code type



Sepf. 15, 1959 F. J. FRANSSON ET AL 2,904,784

RADIO BEACON OF COMPLEMENTARY cons TYPE Filed Aug. 4, 1954 2 Sheets-Sheet 1 MQZZZQ Q.

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- BY QQNMQQM ATTORNEY Sept. 15, 1959 F. J. FRANSSON ET AL 2,904,784

RADIO BEACON OF.COMPLEMENTARY 0003 TYPE Filed Aug. 4, 1954 2 Sheets-Shee t 2 INVENTORB 1 L. BOP/7675 75/? M6 WWW ATTORNEY Patented Sept. 15, 1959 RADIO BEACON or COMPLEMENTARY coma: TYPE Frans J. Fransson, Lidirigo, Sweden, and Toifo Uno Leopold Burmeister, Drumso, Finland, assignors to Svenska Aktiebolaget Gasaccumulator, Lindingo, near Stockholm, Sweden, a corporation of Sweden Application August 4, 1954, Serial No. 447,746

Claims priority, application Sweden August 10, 1953 p 4 Claims. 7, (Cl. 343-'107) Among other kinds of radio beacons there is one which is preferably used as a course indicating radio beacon for indicating course when sailing in to or out from a given harbour. Among the proposals for providing such beacons which have hitherto been made, the type with complementary codes has been most used. This beacon is so arranged that from its antenna there are transmitted two synchronous fields, one of which having a given directive action, for instance by being provided with a frame antenna, and the other one being without marked directive action, for instance being transmitted by a fully non-directive antenna. One of the two fields is reversed in time with a given code and a variation in the characteristic is obtained, so that this is alternatively placed on one side and on the other side of a mean line. On the mean line a constant tone will be heard upon the reversal of phase, whereas on each side of said means line the code with which the phase reversal is made will be heard. Further the code is heard on one side positively, meaning it is composed by sounds corresponding to the said code, whereas, on the other side it is composed negatively, meaning the more or less silent periods between the sounds are forming the code. On the last mentioned side, therefore, the sounds are the complementary code of the one by which the phase reversal is made.

Such complementary code transmitters, however, will not without specific means give a satisfactory indication sharpness. In the first place there are two circumstances determining this sharpness, namely the polar steepness of the composed direction characteristic in the immediate vicinity of the mean line, or in other words, the change of the field intensity with the degrees of bearing, and also the constancy by which the field intensity in the mean line is maintained. Even rather small variations in the constancy of field intensity in the mean line will be confusing and make the determination of the correct course more difiicult. Such variations are emanating by changes of load in the proper moment of phase reversal, the different proposals have been made for avoiding this kind of disturbing lack of constancy of the field intensity. All such means, however, have been expensive and complicated.

It the signal is also modulated, the modulation degree must be kept constant, at least in the mean line or in the vicinity thereof.

The second condition for obtaining good sharpness, namely high steepness in the mean line or in the vicinity thereof, requires that the field intensity relation between the circularly radiating antenna, on the one side, and the strongly directive antenna, on the other side, should be kept small.

If the signal intensity in the mean line, which is also forming the course line, should not be kept constant, it will be more difficult to understand the signals within the approaching range on the one or other side of the course line, and in order to avoid this the above mentioned relation between the field intensities will have to be still further decreased. Now the range of action of the beacon is directly proportional to the field intensity from the preferably circularly radiating antenna, and the consequence therefore will be, that if a great range of action is wanted, steps must be taken which decrease the sharpness of reading, and if a high sharpness of reading is wanted, then steps must be taken which de crease the range of action.

Therefore, there is a need for some means which increase the range of action or the sharpness of reading without the other magnitude simultaneously being decreased. This problem is solved according to the present invention. 7 r

The invention is based upon the observation that short pulses of sound with a high intensity and frequency are well heard by the human ear, even it there are simultaneously strong disturbances. According to the invention, therefore, the transmitted code is divided into a. number of such short pulses of high intensity. The frequency, suitably, should be so high that a plurality of such pulses is contained in the period of time which normally is consumed by one dot contained in the code, and of course then a much higher number of such pulses must form the dash contained in the code.

A very important advantage of the invention is the fact that the code as a whole is composed by pulses interrupted by field free interpulses. It will then be possible to arrange the reversal of the phase position of the one antenna, according to one form of execution of this invention, during the time of such an interpulse, and the means for keeping the load of the transmitter constant during the phase reversal, which has hitherto been very difiicult to provide, can now be left out without decrease of the sharpness of the course indication.

Further it could be mentioned, that hitherto mainly shortwaves for directive radio beacons of this type have been made because long-waves are too strongly disturbed from other transmissions, for instance from coast and approach beacons, ship radio transmitters and so on. The shortwaves, however, have the disadvantage that they are strongly sensitive to reflections from different formations of nature, buildings and so on in the vicinity of the beacon, whereby in some cases there has been observed a considerable error of indication. The radio beacon according to this invention, however, being considerably less sensitive to disturbances dependent upon the just mentioned physiological effect, may use longwaves for the radio beacon in many cases where this could not be regarded possible in the earlier used complementary code beacon types. The wave-length preferably can be between 600 and 2,000 meters.

The use of these wave-lengths in its turn causes a further advantage: The beacons now under consideration have their most important use as approach beacons for smaller vessels, the navigational instruments of which being, for economical reasons, not too advanced. The reason for the said beacons having especially great importance for vessels of this class is that the reception of the beacon signal can take place with a fully conventional radio receiver without directive antenna, goniometer or the like. The vessels in question, as a rule, are provided with a receiver otherwise intended for broadcast radio purposes, but due to the internationally stipulated rules for commercial radio transmission the wave-lengths to which the complementary code beacons were assigned will mostly fall outside of the wave-length ranges which can be received by a broadcast radio receiver. If, on the other hand, the complementary code transmission is arranged on long waves, as a rule there will be no difliculty in be received by a broadcast radio receiver.

For the same reason a high signal intensity can be obtained with a relatively small transmitter system, because the power the transmitter is determined by the mean power used during the transmission.

Finally, the arrangement will be simpler and therefore also more reliable when used, and at the same time it will be cheaper.

In the attached drawings one form of execution of beacon system according to the invention is shown, Fig. 1 showing a wiring diagram of the system, Fig. 2 shows a diagram of the way of working of such beacon system, and Fig. 3 shows a diagram for the signal composition in a course, stated in Fig. 2, and finally Fig. 4 shows certain details present in the arrangement according to Fig. 1.

In Fig. 1, as a matter of simplification, it has been assumed that the two antenna systems. are formed by one first open antenna of practically circular radiation diagram and one frame antenna with a radiation diagram like the figure 8. The open antenna is indicated and the frame antenna 11, and in Fig. 2 the radiation diagram of the open antenna is indicated 12 and the radiation diagram of the frame antenna 13. The two antennas are fed with the same radio frequency voltage, which may be modulated or unmodulated as desired, from a transmitter unit 14 over antenna transformers 15 and 16 respectively. In the feeder conduit to the one antenna, for instance the frame antenna 11, a switch is provided. This switch, which may be of any suitable kind, has been shown schematically in the drawing as a two-armed reversal switch 17 of well-known type, controlled by a relay 18, which is magnetized from the code transmitter 19 in time with the code characteristic to the beacon.

The transmitter 14 is drawn schematically as a blockdiagram, and its construction is well known to the man skilled in the art. A blocking valve in the transmitter is indicated 20, the grid of this valve is connected to a contact 23, subordinated under a relay 24. The counter contact is connected to a strongly negative voltage, so that when this is fed to the grid of the blocking valve 20, this valve is choked. The relay 24 is controlled by means of a pulse generator 25 in a time which is high relatively to the code frequency of the code transmitter 19.

This arrangement functions in the following way: The two antennas 10 and 11 are transmitting fields the direc tion diagrams of which are represented by the curves 12 and 13, respectively, of Fig. 2. In a given position of the phase reverser 17 these direction diagrams are composed into a resulting direction diagram in the form of a curve 26. If the radius of the two diagrams 12 and 13 accidentally is the same, as the case is in Fig. 2, this curve will be a regular cardioidic curve. In practice, it would scarcely be suitable to provide the field intensities of the two antennas in the relation shown in the drawing, and the resulting curve will therefore as a rule more or less deviate from the purely cardioidic form. The form of the curve shown in Fig. 2, however, has been chosen because it will be easier to explain the principle of the invention.

If now the phase of the feeder voltage of the oneantenna is reversed, then the cardiodic curve will also be reversed, so that it is replaced by its image picture 27'. It is then easy to see that a vessel which is situated in the direction 28 will not hear any difference in tone intensity, because both of the cardioidic curves 26 and 27 will in this direction have the same radius vector. If the position of the vessel is changed in such a way that the vessel is situated in the direction 29, the transmission from the beacon stronger when the cardioidic curve 26 is representing the total direction characteristic will be heard, and weaker when the cardioidic curve 27 is representlng the composed direction characteristic, as evidenced from the signal intensity values 30 and 31, respectively. The reversal will take place in time with some known Morse code, for instance the code A--NA-N and so on, so that the cardioidic curve 26 first during a period of time corresponding to the duration of one dash represents the total signal intensity from the beacon, thereafter the cardioidic curve 27 will represent the signal intensity corresponding to the duration of one dot, thereafter again the cardioidic curve 26 will represent the signal intensity during a period of time, which is, however, this time only corresponding to the duration of one dot and thereafter the cardioidic curve 27 will represent the signal intensity during a period of time corresponding to the duration of one dash. Thereafter the code is repeated.

On the vessel in the direction 29 a tone will be heard which is alternatively amplified and weakened, so that the stronger sounds are representing the Morse letter N formed by one dash and one thereafter following dot. If the vessel had instead been situated on the other side of the direction 28, then on the vessel the complementary letter A corresponding to the letter N would be heard, that means, one dot and one thereafter following dash. The person steering the vessel therefore will know if he is on the west side or the east side of the correct course, and he can correct the course of the vessel.

As hitherto described the function of the beacon is known. However, according to the present invention a pulse generator has been provided in such a way that it controls the signal with a frequency which is essentially higher than the code frequency. For instance, one dot may be formed by three pulses as shown in Fig. 3, where the just mentioned code N is played out during the interval of time 32, as it is received by the personnel on board a vessel in the direction 29. If the dash has a duration of: three times the duration of a dot, then the dash will include nine pulses. For the purposes of this description, either a dot or a dash may be referred to as a sign, each sign being made up of a plurality of pulses. Thus if a signal is a Morse letter such as N, it will be made up of two signs, one sign being a dot and the other sign being a dash. The pulse frequency in certain cases should not be so high that it shapes an impression of a tone, but each pulse should be observable separately, although the invention is not limited in this respect.

The reversal of phase now takes place during the interpulses, for instance at the moments of time which are for phase reversal in the one direction indicated 33 and for phase reversal in the other direction indicated 34. Thereby the advantage will be gained that the change of power and load of the transmitter in the moment of the phase reversal does not influence the intensity of the transmitted signal, and one of the most difficult moments of disturbances when receiving the signal from such a complementary code beacon has thereby been eliminated.

It will be evident from the above, that a given degree of synchronism should be present between the function of the pulse generator 25 and the function of the code transmitter 19. This synchronism is ensured by the pulses being fed over a conduit to the pulse counter 36, which may for instance contain a number of switch over relays for alternative switching of the pulses entering by means of said conduit to counter relay chains for alternative counting of three pulses and nine pulses. After every :fully counted number of pulses in one counter relay chain a secondary pulse is transmitted over the conduit 37 to the code mechanism 19,'thereby switching of the phase reverser 17 from the one position into the other one and vice versa.

The arrangement of the pulse generator 25, the pulse counter 36 and the code transmitter 19 is shown by an example in Fig. 4.

The pulse generator will now be described. It can, of course, be shaped in any suitable way, but the pulse generator shown in the drawing has proved in practice to be especially advantageous and reliable. It consists in a primary relay 38 with two windings, 38' and 38". The two windings are wound in difierent directions, so that when current is flowing through both of them, the relay will remain non-energized. The windings are on the one side directly connected to the one terminal of the source of voltage, for instance the minus terminal of an accuiiiulator, whereas, on the other side, the windings are connected to certain means and contact arrangements. Thus the winding 38' is connectedto a resistor 39, which is preferably adjustable. The relay winding 38", in a corresponding way, is connected to a condenser 40. The common conductor 41 from the resistor and the condenser, respectively, is over a contact 42 on the relay 38 and the starting contact 43, which can be operated manually, connected to the positive terminal of the accumulator.

As a matter of order it should now be mentioned that all of the present relay contacts are shown in the drawing in their positions of rest, that means in the positions which they assume at non-energized relay.

The function of the now described part of the pulse generator is as follows: When current is closed to the system at the starter contact 43, immediately a current will run through the relay winding 38', limited by the magnitude of the resistor 39, but simultaneously a load current is created for the condenser 40 through the relay winding 38". As mentioned above, the two windings are directed in such a way, that they counteract each other, and during the load time of the condenser 40 therefore the relay 38 will not be energized. As the condenser approaches its state of full load, however, the load current is decreasing, whereas the current limited by the resistor 39 will remain constant, disregarding that it will of course in moment of closing be subject to a successive increase, choked by the inductance of the relay winding 38'. When the load current has decreased to a given value, the relay 38 will work, and as a consequence thereof the contact 42 is opened, said contact being subordi nated under the relay 38. The current to the relay winding 38' as far as it was caused by the battery voltage therefore ceases at this moment, but the load of the condenser 40 will now be discharged by means of a current through the relay winding 38, said current being at any moment determined by the inductance of this relay winding, the magnitude of the resistor 39 and the remaining charge voltage of the condenser 40. This discharge current passes through the winding 38" in the opposite direction to what it was when charging the condenser, and the attraction forces from the two windings will therefore cooperate, so that the relay 38 will remain attracted during a given time after the contact 42 has been opened. The relay 38 will not fall until the charge voltage of the condenser 40 is practically consumed, and the contact 42 is then closed anew. Then a new charge current to the condenser is created, and the winding 38 will cause energization of the relay, as soon as the condenser is practically fully charged, and a periodically repeated working condition will enter during creation of primary pulses.

For the purposes for which this arrangement should be used, it will, however, often not be sufiiciently exact. It is of especial importance that the pulses are exact, meaning that they have the same duration, and that the duration of the pulse and the duration of the interpulse are like. Even with the most careful adjustment of the relay contacts, the resistor 39 and also of the condenser 40 the fulfilment of these conditions cannot be achieved in practice. For this reason there is also contained in the pulse generator an equalization device, containing the two relays 44 and 45, the latter one of which being provided with two windings 45 and 45". The arrangement is the following one:

The main contact 46 for the group of the two relays 44 and 45 is subordinated under the relay 38 and provided as a switch over contact. In the one of the two alternative branches thereby emanating, there is in series a contact 47, subordinated under the relay 44, further the relay winding 45 and the relay winding 44. The other branch runs to a switch over contact 48, subordinated under relay 45, and of the two thereby emanating alternative branches one also runs to the relay winding of the relay 44, whereas the other one, the branch of working current, is provided to feed the relay winding 45'.

This part of the pulse generator functions in the following way:

When the relay 38 was energized the first time, a current was closed through its contact 46, the non-energized relay closed contact 48 and the relay winding 44 to the positive terminal of the battery, and the relay 44 was energized. It then immediately switches over its contact 4'! and thereby prepares a circuit for the relay winding 45', said relay, however, not yet being energized, because this circuit is still open at the contact 46, A little later on, however, the relay 38 again falls during the primary pulse creation, and now the current is running in series through the relay windings 44 and 45, the relay 45 thereby being energized and switching over its contact 48, which does, however, at this moment cause no action. Simultaneously the contact 48 prepares a circuit through the relay winding 45", said circuit being closed at the next switching over of the primary pulse contact 46 into the energized relay closed position of said contact simultaneously as the circuit through the windings 45 and 44 is opened. The relay 45 therefore remains energized, now by means of its winding 45", but the relay 44 falls, and consequently the contact 47 returns into its nonenergized relay position. When thereafter the relay 38 is de-energized anew during the continuously repeated creation of primary pulses, the energization circuit for the relay winding 45" is opened and all of this part of the pulse generator has returned into position of rest as shown in Fig. 4. At the next energization of the relay 38 the progress is repeated.

It is seen from the above described function, that an halvation of the number of pulses is provided, so that the relay 45 or the relay 44 is attracted for one primary pulse from the relay 38 and is falling back for the next primary pulse from the relay 38. As it is possible to provide, after a stabilized state of heat has emanated in the primary pulse generator part containing the relay 38, each pulse will have a constant duration, it is true that the duration of the pulse is doubled by the function of the relays 44 and 45, but the closing time will be exactly as long as the open time, meaning the so-called pulse-timerelation will be exactly 1:1.

On the relay 44 a switch over contact 49 is provided, and it is this contact which is used as a secondary pulse contact. By means of the conductor 50 the minus voltage is transferred from the battery to the relay 24 in the transmitter 14 and also to the pulse counter 36, which, however, for a purpose which will be mentioned in the following, also is connected to the non-energized closed contact of the pulse contact 49 over a minus voltage carrier conductor 51.

The pulse counter has for its purpose counting the number of secondary pulses which should create one dot or sign in the code transmitted from the beacon. In the example shown in Fig. 3 this number of pulses is three, but it is obvious, that this number is in no way of importance to the invention, and that the number of pulses also can be another one.

The pulse counter contains four relays 52, 53, 54 and 55, the relays 52 and 55 being provided each with one winding, whereas the relays 53 and 54 are provided each with two windings, indicated 53' and 53" or 54' and 54", respectively. The relays 52, 53 and 54 are rapid acting, whereas the relay 55 is slow acting. The coupling is shown in the drawing figure.

The pulse counter functions in the following way: When the relay 44 is energized the first time for starting a pulse, the energized relay closed contact 49 is closed, and a circuit is closed from the minus terminal of the battery over the contact 49, the conductor 50, a non-energized closed contact 56 on the relay 555, the non-energized closed contacts 57 and 58 on the relays 54- and 53, respectively, and the winding of the relay 52 to the positive terminal of the battery. The relay 52 therefore is attractedv The relay 52 is provided with a switch over contact 59, the non-energized relay closed contact consequently now being opened, whereas the energized relay closed contact is closed. This, however, only takes place for preparing a circuit which will later be closed.

When thereafter at the end of the first pulse the relay 44 falls, the non-energized relay closed contact 49 is again closed, and the just described circuit for energization of the relay 52 is opened. The relay 52, however, does not fall, because this relay will be held over a circuit running from the minus terminal of the battery over the nonenergized relay closed contact 49, the conductor 51, a non-energized relay closed contact 60 on the relay 55, the energized relay closed contact 59 of the relay 52 and the relay windings S3 and 52 to the positive terminal of the battery. The relay 52 due to this current being kept in energized state, the relay 5'3 will also be energized.

When the second pulse starts, the energized relay closed contact 49 of the relay 44- is again closed. The circuit through the conductor 58 now as earlier runs through the non-energized relay closed contacts 56 of the relay 55 and 57 of the relay 54, but the relay 53 at this moment being energized, the circuit is fulfilled through the energized relay contact 58 and the relay winding 53', so that the relay 53 will get a holding circuit. Simultaneously the circuit through the relay Winding 53 and the relay Winding 52. is opened, and the relay 52 falls.

The progress continues in the following way: When the second pulse ceases, the non-energized relay contact 49 is again closed, and a circuit is running from the minus terminal over the non-energized relay closed contact of said relay, the conductor 51, the non-energized relay closed contact 6%, the non-energized relay closed contact 60, the non-energized relay closed contact 59, the energized relay closed contact 61 and the windings 54 and' 53. in spite of the energization circuit for the relay 53 being opened, the relay 53 does not fall, but the relay 54 will be attracted. It is true that this circuit will be opened at the entering of the third pulse so that the relay 53 now falls, but a holding circuit will be closed for the relay 54 frorn't'ne minus terminal over the energized relay closed contact 49, the conductor 50, the non-energized relay closed contact 56, theenergized relay closed contact 57 and the winding 54 to the plus terminal. When the third pulse ceases, this energization circuit for the relay 54wi1l be opened, but it will be replaced by a holding circuit, which includes also the winding of the relay 55. This circuit runs from the minus terminal over the contact 49, the conductor 51, the non-energized relay closed contacts 6t 59 and61 and the energized relay closed contact 62 and the windings 55 and 54.

The relay 55, however, as mentioned above, is slow acting and consequently it will last a given time until its contact 66 is opened. When this takes place, simultaneously the holding circuit for the winding 54' of the relay 54 is opened, and all of the relay chain is returning into its initial state shown in the drawing. The relay chain thereby has counted three secondary pulses, and it is now prepared to repeat its counter operation for the next number of three secondary pulses. During the time when the relay 55' was attracted however, a time which due to the slow action of this relay can include up to several deciseconds, its contact 63 was switched over into its energized relay position. The contact 63 functions as a pulse contact for the pulses, which are at the end of three consecutive secondary pulses given off to the code mechanism 19 for determining its function. The last-mentioned pulses in the following are indicated as tertiary pulses.

The code mechanism is built in the same way as the pulse counter 36, only the number of relays is greater. A full code includes 24 secondary pulses, see Fig. 3, or in other words eight tertiary pulses. The counter relay chain 8 'I in the code mechanism consists in a starter relay 64, corresponding to the relay 52 of the secondary pulse counter relay chain, said relays 65-71 being provided with two windings and corresponding to the two relays of similar kind 53 and 54 in the secondary pulse counter relay chain and a final relay 72, corresponding to the final relay 55. The coupling is the same as in the counter relay chain already described, and it would therefore be enough here to indicate the state of the different relays:

Interval: Energized relays 1. Pulse 64 1. Interpulse 64 and 65 2. Pulse 65 2. Interpulse 65 and 66 3. Pulse 66 3. Interpulse 66 and 67 4. Pulse 67 4. Interpulse 67 and 68 5. Pulse 68 5. Interpulse 68 and 69 6. Pulse 69 6. Interpulse 69 and 70 7. Pulse 70 7. Interpulse 70 and 71 8. Pulse 71 '8. Interpulserelay 72 short time energization,

thereafter no relay energized.

It is now easy to see how on basis of the relays 6472 the code transmission can be arranged so'that current is fed to the relay 18 in time with the desired code A-NA-N and so on. Looking at Fig. 3 it is seen that the relay shall be without current during the three first tertiary pulses, that it shall be switched over during the third tertiary interpulse and carry current during the fourth tertiary pulse, again being switched over during the fourth tertiary interpulse, so that it is without current during the fifth tertiary pulse, thereafter again being switched over into current carrying state in which it shall remain during the sixth, seventh and eighth tertiary pulses and finally be switched over into current free state for repetition of this operation.

During the run of the third tertiary interpulse, however, the relay 67 is attracted, and consequently the conductor 73 for feeding voltage to the relay 18 is carried over an energized relay closed contact 74 on the relay 67. This relay, however also remains energized during the fourth interpulse, and if the adjustment of the relay should not be good, it might possibly occur that the switching over into current free state of the re lay 18 would happen so late that a fraction of the fifth pulse would be transmitted. In order to prevent this, the circuit is also carried over a non-energized relay closed contact 75 of the relay 68, which is already attracted during the run of the fourth interpulse, so that the relay 13 is reliably without current before the fifth pulse is starting.

During the run of the fifth pulse, the relay 69 is again 64-72 are de-energized. The relay 18 consequently will work in the given time.

Of course, the invention is not limited to the specific form of execution shown in the drawing and described above, but different modifications may occur within the frame of the invention. For instance, the code may be another one than ANA-N, and the number of primary pulses during the run of one secondary pulse may be another than three. pulse mechanism and the pulse counter or the code mech- It is not even required that the anism, respectively, be made as counter relay chains, but any other type of construction suitable for the purpose may be used, for instance rotating slip contacts or the like.

What is claimed is:

1. A radio beacon comprising, in combination, a pair of antennas having different radiation patterns, a pulse generator for simultaneously transmitting a pulse over said antennas, a phase shifter for reversing the phase of the pulse transmitted to said antennas in time with a given signal composed of at least one sign, the radiation patterns of the antennas in synchronized and reversed phase producing overlapping cardioidic curves intersecting along a straight line, each sign comprising a plurality of pulses.

2. A radio beacon according to claim 1 wherein the pulse frequency is low whereby the signals are audible separately without giving a tone impression.

3. A radio beacon according to claim 1 including a pulse counter connected to said pulse generator for triggering said phase shifter.

4. A radio beacon according to claim 1 wherein said pair of antennas comprise an open and a frame antenna producing different radiation patterns.

References Cited in the file of this patent UNITED STATES PATENTS 

